Patterns of uveitis in the middle East and europe.

PURPOSE
To compare the patterns of uveitis, emphasizing similarities and discrepancies, in the Middle East and Europe.


METHODS
Six articles reporting uveitis patterns from the Middle East including a total of 2,693 cases, and seven articles with a sum of 4,379 cases from Europe were analyzed and patterns in each region were defined and compared.


RESULTS
In both regions, uveitis was most commonly seen in the fourth decade of life with anterior uveitis being the most common anatomical form. Idiopathic cases accounted for the majority of anterior and intermediate uveitis; toxoplasmosis was the most frequent entity in posterior uveitis while Behcet's disease and idiopathic forms were the next most common causes in the Middle East and in Europe, respectively.


CONCLUSION
Since patterns of uveitis differ in various geographic regions, discovering these patterns would be helpful for the diagnosis and treatment of this broad category of conditions. This necessitates applying a universal diagnostic classification system to enable accurate comparisons.


INTRODUCTION
Uveitis accounts for 5-20% of legal blindness in Europe and the United States 1 , therefore recognition of the prevalence and patterns of this diverse group of ocular disorders is necessary for their diagnosis and treatment.
Due to the varying prevalence of infectious (e.g. tuberculosis and toxoplasmosis) and noninfectious (e.g. Behçet's disease) entities in different parts of the world, one would expect variability in the prevalence and patterns of uveitis. This variability may be influenced by multiple factors including race and genetic background, environmental factors, referral patterns, and diagnostic criteria and facilities.
For instance, in the US, the four most common forms of uveitis include acute anterior uveitis associated with ankylosing spondylitis, sarcoidosis, cytomegalovirus retinitis, and toxoplasmosis. [2][3][4][5] In Japan, the incidence of Behçet's disease, Vogt-Koyanagi-Harada (VKH) syndrome, and toxoplasmosis have shown an apparent decrease, while the incidence of sarcoidosis and acute anterior uveitis are increasing. [6][7][8] In the Indian subcontinent, toxoplasmosis, VKH syndrome, and idiopathic anterior uveitis are most frequently observed. 9,10 In Africa, AIDS, herpes zoster ophthalmicus, toxoplasmosis, tuberculosis (TB), rheumatoid arthritis, and onchocerciasis are the most JOURNAL OF OPHTHALMIC AND VISION RESEARCH 2011; Vol. 6,No. 4 commonly associated diseases. 11 The purpose of this study was to compare patterns of uveitis in Europe with that in the Middle East, and to highlight similarities and disparities.

METHODS
Six articles [12][13][14][15][16][17] from the Middle East including a sum of 2,693 cases and seven articles from Europe [18][19][20][21][22][23][24] with a total number of 4,379 cases were reviewed and compared. First, articles originating from the Middle East underwent review and data analysis, then they were assessed as a whole and general statistics for this region were extracted. European articles were analyzed similarly followed by comparison of data from the two regions.
Except for the Finnish study 20 , which was community-based, all other reports were obtained from tertiary referral centers. In the study performed in Israel 17 , the criteria for classification of uveitis were not mentioned. Standardization of uveitis nomenclature group (SUN) and the criteria used by Perkins (1961) were applied in Turkey 14 and Finland 20 r e s p e c t i v e l y a n d t h e r e s t h a d u s e d t h e international uveitis study group (IUSG) criteria for this purpose.
Having been classified as an idiopathic and independent disease in some articles, all cases of pars planitis were considered as idiopathic for uniformity. An article from Israel 17 only reviewed chronic uveitis cases and therefore did not represent a comprehensive report from that region. Statistical data from some articles were not classifiable at all and were thus excluded from calculations. For example, the Brussels study 22 did not include anterior uveitis and in studies from Poland 19 , Italy 21 and Saudi Arabia 15 the number of cases in anatomic subgroups was not mentioned.
To present data, we used mean ± standard deviations (SDs) and frequencies (percentage). To compute these values we used weighted means proportional to sample size of a particular paper. Whenever there was no information about a particular item, we disregarded that particular data. All statistical analyses were performed using SPSS software version 17.0 (SPSS Co., Chicago, USA).

Mean age of participants in Middle Eastern
and European studies was 35.2 and 39.1 years, respectively. Male subjects comprised 52% of cases in Middle Eastern and 49.4% of subjects in European studies. There was no significant difference in terms of age and sex between Middle Eastern and European studies; both study groups reported the fourth decade of life as the most common age for presentation of uveitis (Table 1).

DISCUSSION
Limitations of epidemiological studies on uveitis stem from a variety of factors including heterogeneity of diagnostic criteria and workup, lack of uniform classification systems or precise definitions, and the effects of referral and selection bias. These factors render comparison of epidemiological studies from different regions and populations difficult. Most uveitis studies convey data obtained from tertiary referral centers rather than population-based information. More complicated and severe forms of pan-and posterior uveitis may be over-represented at referral centers; in contrast, primary care and population-based studies tend to report less severe cases such as anterior uveitis.
Average age and male to female ratio did not differ significantly between Middle Eastern and European studies (35.2 versus 39.1 years, and 52% versus 49.4%, respectively).
The most frequent anatomic forms, in order    15,16 and Israel 17 stood next. In one Saudi Arabian study 16 , TB was rather frequent. As mentioned above, in all European studies, idiopathic cases were the most common group; in the Italian study 18 , herpes viruses, TB and FHIC ranked next, and in the Rome 21 and Amsterdam 23 studies, FHIC was frequently reported. In comparison, Behçet's disease was more frequent in the Middle East while TB, FHIC and herpes viruses were more frequent in Europe.
Regarding posterior uveitis, in the Middle East, toxoplasmosis was the most frequently reported cause in Iran 12 , Ankara 13 and Saudi Arabia 15,16 , while Behçet's disease in Turkey 14 , and idiopathic forms in Israel 17 were the most prevalent causes. Noteworthy entities were toxocariasis, FHIC, and ARN in Iran 12 , VKH syndrome in Turkey 14 and sympathetic ophthalmia in Israel 17 . In European studies, toxoplasmosis was also the most common cause of posterior uveitis in Italy 18 and Amsterdam 23 ; other causes of considerable importance included ARN in Amsterdam 23 , toxocariasis in Rome 21 , and Behçet's disease in Brussels 22 . Toxoplasmosis and idiopathic cases were more frequent in Europe, while other causes were more common in the Middle East.
Concerning panuveitis, in Middle Eastern studies, Behçet's disease was consistently the most frequent cause in Iran 12 , Turkey 14 , Ankara 13 , and Israel 17 . In Israel 17 , toxoplasmosis and sympathetic ophthalmia were rather frequent but idiopathic cases were less common. VKH syndrome in Iran 12 and Saudi Arabia 15 , MCP in Iran 12 , and sarcoidosis in Saudi Arabia 16 were also common. In all European studies except for Finland 20 , idiopathic cases were most common, but Behcet's disease in Italy 18 and Rome 21 , sarcoidosis in Amsterdam 23 , VKH syndrome in Italy 18 , and toxoplasmosis in Finland 20 were other prominent causes. In general, Behçet's disease and VKH were more common in the Middle East, while idiopathic cases, toxoplasmosis, and sarcoidosis were more frequent in Europe.
In terms of intermediate uveitis, idiopathic cases held the largest share in both European and Middle Eastern reports. Eye-catching prevalence rates were noted for sarcoidosis in Iran 12 and Turkey 13 , multiple sclerosis in Saudi Arabia 16 and Iran 12 , TB in Saudi Arabia 16 and Behçet's disease in Ankara 13 . In Europe, other common causes of intermediate uveitis were sarcoidosis and multiple sclerosis in Amsterdam 23 .
Overall, in both geographic regions, idiopathic uveitis was the most common form of intraocular inflammation; in the Middle East, Behçet's disease and toxoplasmosis, and in Europe, toxoplasmosis and herpes viruses ranked second and third. Behçet's disease, VKH and sympathetic ophthalmia were more common in the Middle East while toxoplasmosis and HLA-B27 associated disorders were more frequent in Europe. Considering infectious causes, toxoplasmosis in Europe and TB in the Middle East were relatively more prevalent but herpes viruses did not show any prominent differences in prevalence.
Since uveitic entities follow different patterns in different regions and are influenced by a variety of factors, epidemiologic studies can help improve their diagnosis and treatment. Adoption of a universal classification systems and population-based studies in all countries may provide more reliable data for comparisons among different areas.

Conflicts of Interest
None.